The typical human body contains about 206 bones and approximately 640 muscles resulting in about 230 moveable and semi-movable joints. Anatomists generally define a joint as any instance where two or more bones connect. They are constructed to allow movement of the skeleton and/or support of the body. Joints are usually classified structurally (i.e., fibrous, cartilaginous, or synovial); functionally (i.e., synarthrothis, amphiarthrosis, or diarthrosis); and biomechanically (i.e., simple, compound, or complex).
Synovial joints (synonymous with “diarthrosis”) are the joints most people commonly think of when they hear of someone having injured a joint. Synovial joints include, but are not limited to, the ankle, knee, hip, shoulder, elbow, and wrist. Synovial joints are extremely complex structures containing numerous parts. A typical synovial joint comprises at least two bones, tendons connecting muscle to bone, ligaments connecting bone to bone, cartilage to cushion bones, specialized cells to create synovial fluid, and specialized tissue to surround and protect the interior of the joint (the “joint capsule”). Other possible components (depending on the joint) include articular discs and meniscus. Each joint is also innervated in some manner.
Because synovial joints are so complex, any damage to a single component can lead to decreased functionality of that joint. For example, professional athletes commonly tear or completely rupture their anterior cruciate ligament (ACL) which is a piece of fibrous tissue in the knee joint that helps keep the ends of femur and the tibia in their proper position during movement. Catastrophic injuries such as motorcycle accidents can essentially rip a joint apart by rupturing multiple components (i.e., ligaments, tendons, joint capsule).
Fortunately, modern surgical procedures can repair or replace a torn ACL and even whole knees. However, even with the surgical miracles at our disposal, some sufferers of joint injury never fully recover from the damage and experience some form of pain, such as arthritic pain, for the rest of their lives. Some sufferers of joint injury also experience some permanent loss of function in the joint or limb and require orthopedic support for that joint for the rest of their life. Long term pain management techniques including acupuncture, non-steroidal anti-inflammatory medications, and/or controlled medications may be necessary in some instances.
Many injured individuals awaiting surgical intervention, or those that never fully recover from joint injury, use orthotic devices to reduce stress on the joint and/or provide additional structural support and/or reduce pain. The area of orthotics is filled with numerous devices designed to provide support and protection to all of the major joints (i.e., knee, elbow, ankle, etc.). The vast majority of these known devices provide at least some degree of support, protection, and/or pain relief to a user. However, none of the known devices address a variable that has been associated with increased joint pain—changes in atmospheric pressure (aka barometric pressure).
All readers probably know of at least one individual who claims that an arthritic or injured joint becomes painful “when a storm is approaching” or an older relative who predicts the weather based on how their knee feels. There is no shortage of anecdotal evidence that a drop in atmospheric pressure, such as the drop that often accompanies a storm system, is somehow related to an increase in joint pain.
Over the years, several scientific studies have attempted to better quantify the apparent relationship between joint pain and atmospheric pressure changes. One such study consisted of 16 patients with rheumatoid arthritis, 24 patients with osteoarthritis, 11 patients with inflammatory arthritis, and 11 patients with fibromyalgia joint pain. 25% the patients with rheumatoid arthritis, 83% of the patients of with osteoarthritis, 64% of the patients with inflammatory arthritis, and 77% of the patients with fibromyalgia reported sensitivity to weather changes. Guedj and Weinberger, “Effects of Weather Conditions on Rheumatic Patients”, Annuals of Rheumatic Diseases, 1990; 49:158-159.
Although the cause and effect between decreased atmospheric pressure and increased joint pain is likely multi-factorial, it is thought that one potential cause is the expansion of the joint capsule which is innervated. If a joint is injured or arthritic, the tissue within and surrounding the joint may become inflamed (i.e., thickened, swollen, etc.). This increases pressure within the joint. Over time the body may become acclimated to the increased joint pressure during periods of normal or high atmospheric pressure. However, one theory for weather related joint pain is that as the atmospheric pressure decreases there is less pressure “outside” of the joint offsetting the pressure “within” the joint. The joint capsule then expands, stretching the tissue and stimulating pain receptors. Again, the above explanation is only a theory but people have reported a decrease in pain sensation when slight additional pressure is applied to an injured joint during times of low atmospheric pressure.
Accordingly, there is a need for an orthotic which addresses the relationship between changes in atmospheric pressure and the pain/discomfort experienced by those with joint pain.